Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with agraphical user interface in accordance with the first embodiment; and,

FIG. 2 is a front view of a second embodiment thereof.

The outermost broken lines illustrate a display screen or portionthereof and form no part of the claimed design. The remaining brokenlines, illustrating portions of the graphical user interface, form nopart of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.